Numbers 9:5

And they kept the passover on the fourteenth day... — There is no mention here of the observance of the feast of unleavened bread for seven days, as it was enjoined in Exodus 12:18. It might not have been practicable to obtain a sufficient quantity of flour to last so large a number of people for seven days, though it may have been easy to procure from Midian or elsewhere a sufficient quantity for one meal.